WDM Path Differential Delay Management for Geographically Dispersed Servers
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Solution Overview
Problem
Conventional systems for geographically diverse servers connected via wavelength division multiplexed (WDM) systems face challenges in accurately determining and managing transmit/receive path differential delay, leading to inaccurate time stamps and inadequate performance in disaster recovery applications like IBM's Geographically-Dispersed Parallel Sysplex (GDPS), due to asymmetrical fiber lengths and the presence of optical amplifiers and multiplexing schemes.
Innovation Solution
The implementation of absolute time references, such as GPS time references, and selective buildout delays, specifically using FIFO buffers, to measure and compensate for differential delays between transmit and receive paths, ensuring synchronization and meeting the 10 microsecond requirement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If geographically diverse servers are connected via WDM systems over long distances, then system availability and disaster recovery capability are improved, but transmit/receive path differential delay becomes unmanageable and time stamp accuracy deteriorates
Solution Approach 1:
The patent replaces conventional electronic timing synchronization mechanisms with optical timing synchronization using WDM systems. By utilizing optical carriers and optical path timing measurement, the system achieves accurate differential delay measurement over geographically dispersed connections without the limitations of electronic signal degradation over long distances
Solution Approach 2:
The patent introduces an intermediary timing synchronization mechanism that uses optical reference signals transmitted through the WDM system to establish a common timing reference between geographically diverse servers. This intermediary optical timing reference enables accurate differential delay measurement and compensation without direct electronic connection between remote sites
2Adaptability or versatility
If asymmetrical fiber lengths and optical amplifiers are used in WDM systems, then system adaptability and deployment flexibility are improved, but differential delay measurement precision deteriorates
Solution Approach 1:
The patent changes the measurement parameter from electronic signal timing to optical signal timing. By measuring differential delay using optical reference signals transmitted through the same WDM path as data signals, the system accurately captures the actual timing differences introduced by asymmetrical fiber lengths and optical amplifiers, enabling precise compensation despite physical path variations
Solution Approach 2:
The patent uses optical reference signals as copies of the data signal path to measure differential delay. These reference signals traverse the exact same optical path including all amplifiers and multiplexing elements, creating a timing template that accurately represents the actual signal transmission characteristics without requiring separate measurement paths
3Device complexity
If conventional timing synchronization methods are used in geographically diverse systems, then device complexity is reduced, but transaction processing consistency deteriorates
Solution Approach 1:
The patent makes the WDM system itself serve multiple functions: data transmission and timing synchronization. The same optical infrastructure that carries data signals also carries timing reference signals, eliminating the need for separate synchronization hardware and reducing overall system complexity while ensuring transaction processing consistency through accurate timing
Data Source
AI summary
The present disclosure relates to systems and methods for geographically-diverse redundant servers and the like interconnected via wavelength division multiplexed (WDM) systems with managed path differential delay of the WDM systems. The present disclosure provides transport systems and methods incorporating absolute time references, such as global positioning system (GPS) time references and/or the like, and selective buildout delays, such as first-in, first-out (FIFO) buildout delays and/or the like. In one exemplary embodiment, the transport systems and methods of the present invention are used in conjunction with the International Business Machine Corporation (IBM) Geographically-Dispersed Parallel Sysplex (GDPS) integrated, automated application and data availability solution to meet and/or exceed the associated 10 microseconds transmit/receive path differential delay requirement. Other comparable uses are also contemplated herein, as will be obvious to those of ordinary skill in the art.